This site calculates the "performance rating" for players of the World of Tanks massively-multiplayer online game (EU, US, RU).
It is currently in beta stage (early release).
It is a calculated value assessing the player skill, based on an assessment of the tanks the player is playing, the damage dealt and the win rate.
It is a more accurate assessment of player skill, as it focuses on two values which are hard to boost together - damage dealt, and win rate (CW/TC can boost win rate but will lower damage dealt). A player generally cannot improve these two values without directly helping his team, thus there is no way to selfishly inflate the performance rating values.